Investigation into the Synthesis, Bioactivity, and Mechanism of Action of the Novel 6-Pyrazolyl-2-picolinic Acid as a Herbicide.

A series of new 4-amino-3,5-dicholo-6-(5-aryl-substituted-1H-pyrazol-1-yl)-2-picolinic acid compounds were designed and prepared to discover herbicidal molecules. The inhibitory activities of all new compounds against the root growth ofArabidopsis thaliana were assayed. On the whole, the new synthesized compounds displayed good inhibition effects and had excellent herbicidal activities on root growth of weed at 500 µM. Importantly, a selection of compounds demonstrated comparable herbicidal properties to picloram. At the dosage of 250 g/ha, most of the compounds showed a 100% postemergence herbicidal activity to control Chenopodium album and Amaranthus retroflexus. Using compound V-2, the mechanism of action was investigated based on a phenotype study using AFB5-deficient Arabidopsis thaliana. It was found that the novel 6-pyrazolyl-2-picolinic acids were auxinic compounds. In addition, it was proposed that V-2 may be an immune activator due to its upregulation of defense genes and the increased content of jasmonic acid.

Study on Design, Synthesis and Herbicidal Activity of Novel 6-Indazolyl-2-picolinic Acids.

Thirty-eight new 4-amino-3,5-dicholo-6-(1H-indazolyl)-2-picolinic acids and 4-amino-3,5-dicholo-6-(2H-indazolyl)-2-picolinic acids were designed by scaffold hopping and synthesized to discover potential herbicidal molecules. All the new compounds were tested to determine their inhibitory activities against Arabidopsis thaliana and the root growth of five weeds. In general, the synthesized compounds exhibited excellent inhibition properties and showed good inhibitory effects on weed root growth. In particular, compound 5a showed significantly greater root inhibitory activity than picloram in Brassica napus and Abutilon theophrasti Medicus at the concentration of 10 µM. The majority of compounds exhibited a 100% post-emergence herbicidal effect at 250 g/ha against Amaranthus retroflexus and Chenopodium album. We also found that 6-indazolyl-2-picolinic acids could induce the up-regulation of auxin genes ACS7 and NCED3, while auxin influx, efflux and auxin response factor were down-regulated, indicating that 6-indazolyl-2-picolinic acids promoted ethylene release and ABA production to cause plant death in a short period, which is different in mode from other picolinic acids.

Parallel kinetic resolution of aziridines via chiral phosphoric acid-catalyzed apparent hydrolytic ring-opening.

We report a chiral phosphoric acid catalyzed apparent hydrolytic ring-opening reaction of racemic aziridines in a regiodivergent parallel kinetic resolution manner. Harnessing the acyloxy-assisted strategy, the highly stereocontrolled nucleophilic ring-opening of aziridines with water is achieved. Different kinds of aziridines are applicable in the process, giving a variety of enantioenriched aromatic or aliphatic amino alcohols with up to 99% yields and up to >99.5 : 0.5 enantiomeric ratio. Preliminary mechanistic study as well as product elaborations were inducted as well.

Design, Synthesis, Herbicidal Activity, and Structure-Activity Relationship Study of Novel 6-(5-Aryl-Substituted-1-Pyrazolyl)-2-Picolinic Acid as Potential Herbicides.

Picolinic acid and picolinate compounds are a remarkable class of synthetic auxin herbicides. In recent years, two new picolinate compounds, halauxifen-methyl (ArylexTM active) and florpyrauxifen-benzyl (RinskorTM active), have been launched as novel herbicides. Using their structural skeleton as a template, 33 4-amino-3,5-dicholor-6-(5-aryl-substituted-1-pytazolyl)-2-picolinic acid compounds were designed and synthesized for the discovery of compounds with potent herbicidal activity. The compounds were tested for inhibitory activity against the growth of Arabidopsis thaliana roots, and the results demonstrated that the IC50 value of compound V-7 was 45 times lower than that of the halauxifen-methyl commercial herbicide. Molecular docking analyses revealed that compound V-7 docked with the receptor auxin-signaling F-box protein 5 (AFB5) more intensively than picloram. An adaptive three-dimensional quantitative structure-activity relationship model was constructed from these IC50 values to guide the next step of the synthetic strategy. Herbicidal tests of the new compounds indicated that compound V-8 exhibited better post-emergence herbicidal activity than picloram at a dosage of 300 gha-1, and it was also safe for corn, wheat, and sorghum at this dosage. These results demonstrated that 6-(5-aryl-substituted-1-pyrazolyl)-2-picolinic acid compounds could be used as potential lead structures in the discovery of novel synthetic auxin herbicides.

Design, Synthesis, Fungicidal and Insecticidal Activities of Novel Diamide Compounds Combining Pyrazolyl and Polyfluoro-Substituted Phenyl into Alanine or 2-Aminobutyric Acid Skeletons.

Thirty novel diamide compounds combining pyrazolyl and polyfluoro-substituted phenyl groups into alanine or 2-aminobutyric acid skeletons were designed and synthesized with pyflubumide as the lead compound to develop potent and environmentally friendly pesticides. The preliminary bioassay results indicated that the new compounds containing the para-hexa/heptafluoroisopropylphenyl moiety exhibit fungicidal, insecticidal, and acaricidal activities. This is the first time that the para-hexa/heptafluoroisopropylphenyl group is a key fragment of the fungicidal activity of new N-phenyl amide compounds. Most of the target compounds exhibited moderate to good insecticidal activity against Aphis craccivora at a concentration of 400 µg/mL, and some showed moderate activity at a concentration of 200 µg/mL; in particular, compounds I-4, II-a-10, and III-26 displayed higher than 78% lethal rates at 200 µg/mL. Compound II-a-14 exhibited a 61.1% inhibition at 200 µg/mL for Tetranychus cinnabarinus. In addition, some of the target compounds exhibited good insecticidal activities against Plutella xylostella at a concentration of 200 µg/mL; the mortalities of compounds I-1, and II-a-15 were 76.7% and 70.0%, respectively. Preliminary analysis of the structure-activity relationship (SAR) indicated that the insecticidal and acaricidal activities varied significantly depending on the type of substituent and substitution pattern. The fungicidal activity results showed that compounds I-1, II-a-10, II-a-17, and III-26 exhibited good antifungal effects. Enzymatic activity experiments and in vivo efficacy of compound II-a-10 were conducted and discussed.

Study on Optimal Parameter and Target for Pulsed-Field Ablation of Atrial Fibrillation.

Pulsed-field ablation (PFA) had potential advantages in atrial fibrillation ablation, and we aim to confirm the optimal parameter and target of PFA for atrial fibrillation. Two ablation modes in vitro of single-cell system (ablation in electrode cup) and monolayer cell system (ablation in inserts with electrode tips) were established to perform PFA for myocardial cell H9C2 and smooth muscle cell A7r5. Ablation effect, calcium ion influx, the expression of Cx45, and surface morphological change were observed. Three Bama minipigs were used to verify the in vivo ablation effect of PFA. In monolayer cell system, H9C2 was significantly sensitive to PFA compared with A7r5, with shrinking of the whole monolayer. The ablation effect of bidirectional pulse was weaker than that of the two mono-polar pulses. Expressed Cx45 proteins were increased in H9C2 but decreased in A7r5 cells. Bidirectional PFA performed on Bama minipigs was able to effectively block electrical activity from the pulmonary vein to the atrium with week muscle contraction, not generating pulmonary vein stenosis. Bidirectional PFA was able to significantly ablate myocardial cells, maintain cell-cell connection, and reduce muscle contraction, which was a kind of optimized PFA strategy for atrial fibrillation.

Design, synthesis and mode of action of novel 3-chloro-6-pyrazolyl picolinate derivatives as herbicide candidates.

BACKGROUND: Picolinate/picolinic acid compounds are an important class of synthetic auxin herbicides. To explore the herbicidal activity of 6-pyrazolyl picolinate compounds, a series of 3-chloro-6-pyrazolyl-picolinate derivatives was designed and synthesized. RESULTS: Twenty-five 3-chloro-6-pyrazolyl-picolinate derivatives synthesized were tested for herbicidal activity and the IC50 value of compound c5 to the growth of Arabidopsis thaliana root was 27 times lower than that of the commercial herbicide clopyralid. Compound c5 displayed better post-emergence herbicidal activity and broader (Picloram, Clopyralid, Aminopyralid) herbicidal spectrum at a dosage of 400 g ha-1 in comparison with clopyralid; it also was safe to wheat and maize at this dosage. Arabidopsis thaliana phenotypes and expression of auxin-response genes demonstrated that compound c5 might be a novel auxin-type herbicide. Molecular docking analyses revealed that compound c5 had stronger binding ability to receptor AFB5 (auxin signaling F-box protein 5) than clopyralid. CONCLUSION: These 6-pyrazolyl picolinate compounds could be used as potential lead structures for the discovery of a novel synthetic auxin herbicide. © 2021 Society of Chemical Industry.

A highly selective and sensitive fluorescence probe for a specific binding site on insect ryanodine receptors.

There is a significant need to study the binding of active compounds to the specific sites on insect ryanodine receptors (RyRs) that are the targets of two novel classes of diamide insecticides to which insects are becoming increasingly resistant. Here, we describe a rapid assay to study the action of potential compounds on the flubendiamide (Flu) binding site of insect RyRs that uses a fluorescence polarization assay with the fluorescence probe Flu-R-L that we synthesized. The IC50 of Flu for inhibiting probe binding on insect RyR was 18.82 ng/mL. The binding of 86 novel phthalic diamide derivatives on insect RyRs was studied using this newly established assay, and the compounds that exhibited high-affinity binding in the assay also possessed in vivo insecticidal activity against Plutella xylostella. Thus, Flu-R-L is a highly selective and sensitive fluorescence probe for studying the binding affinity of novel compounds to the Flu binding site of insect RyRs. The assay based on Flu-R-L is a rapid, accurate, and sensitive method for the screening of potentially bioactive molecules that bind specifically to insect RyRs.

Enantioselective growth inhibition of the green algae (Chlorella vulgaris) induced by two paclobutrazol enantiomers.

Enantiomers of chiral pesticides usually display different toxic effects on non-target organisms in surrounding environment, but there are few studies on its enantioselective toxicity of paclobutrazol to aquatic organisms such as Chlorella vulgaris (C. vulgaris). In this study, the enantioselective bioaccumulation and toxicities, such as acute toxicity and oxidative stress, of the racemate, (2S, 3S)-enantiomer (S-enantiomer) and (2R, 3R)-enantiomer (R-enantiomer) of paclobutrazol to the C. vulgaris cells were investigated. The results showed that the algae cells were able to accumulate the paclobutrazol in a short time, while this bioaccumulation had no enantioselective distinction between the two enantiomers during biological metabolism. However, the racemate and two enantiomers of paclobutrazol significantly inhibited the growth of C. vulgaris, displayed different median lethal concentrations. The photosynthetic pigments, photosynthesis-related genes as well as antioxidation-related biomarkers in treated C. vulgaris were also investigated. In general, R-enantiomer was found to be more toxic to C. vulgaris cells than its racemate and S-enantiomer. Additionally, transmission electron microscopy (TEM) analysis showed the R-enantiomer caused more serious changes than S-enantiomer. Moreover, contents of two plant hormones (gibberellin, GA and indoleacetic acid, IAA) were determined in treated C. vulgaris. Higher paclobutrazol concentrations caused lower IAA contents significantly. Nevertheless, the two enantiomers showed no enantioselective effects on the biosynthesis of GA in C. vulgaris. Our results are helpful to understand the enantioselective effects of paclobutrazol enantiomers on non-target organisms, and useful for evaluating their environmental risks.

A monoclonal antibody-based indirect competitive enzyme-linked immunosorbent assay for flubendiamide detection.

Flubendiamide (FD), the first commercial phthalic acid diamide that targets insect ryanodine receptor (RyRs), has played an important role in pest management. With its extensive worldwide application, a rapid and convenient method to detect its existence in the environment is necessary. In this study, an indirect competitive enzyme-linked immunosorbent assay (icELISA) was developed to analyse FD residue on environmental and food samples. The established icELISA showed a half maximal inhibition concentration (IC50) of 17.25 µg L-1, with a working range of 4.06-103.59 µg L-1 for FD, and showed no cross-reactivity with chlorantraniliprole, cyantraniliprole, and several FD analogues. Average FD recoveries from spinach, tap water, and soil samples were 89.3-112.3%, 93.0-102.1%, and 86.9-97.6%, respectively. Meanwhile, FD detection results of icELISA were compared with those of ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The comparable results verified that icELISA was suitable for rapid detection of FD residue in environmental and agricultural samples.

Design, Synthesis, and Biological Activities of Novel 1,3,5-Trimethylpyrazole-Containing Malonamide Derivatives.

New 1,3,5-trimethylpyrazole-containing malonamide derivatives based on pyflubumide were designed, synthesized, and characterized using ¹H-NMR, 13C-NMR, and high-resolution mass spectra (HRMS). The results of preliminary bioassays showed that the target compounds possessed good activities against Tetranychus cinnabarinus, Plutella xylostella, and Aphis craccivora. Most of the target compounds exhibited moderate to good acaricidal activity against Tetranychus cinnabarinus at a concentration of 400 µg/mL, and some showed moderate activity at a concentration of 200 µg/mL; in particular, compounds 8m and 8p exhibited 70.0% mortality. In addition, some of the target compounds exhibited good insecticidal activities against Plutella xylostella at a concentration of 200 µg/mL, especially compounds 8i and 8o, which achieved 100.0% mortality at a concentration of 100 µg/mL. Interestingly, some of the target compounds exhibited potent anti-aphid activity against Aphis craccivora at a concentration of 200 µg/mL; furthermore, compounds 8p and 8q demonstrated 100.0% anti-aphid activity at a concentration of 50 µg/mL. The preliminary analyses of the structure⁻activity relationships (SAR) indicated that the acaricidal and insecticidal activities varied significantly depending on the type of substituent and substitution pattern, which provides guidance for the further investigation of such structural modifications.

The insecticide chlorantraniliprole is a weak activator of mammalian skeletal ryanodine receptor/Ca2+ release channel.

Chlorantraniliprobe (Chlo), a potent insecticide, demolishes intracellular Ca2+ homeostasis of insects by inducing uncontrolled Ca2+ release through ryanodine receptors (RyRs). Chlo is lethal to insects but has low toxicity to mammals. In this study, we investigated the effects of Chlo on RyR1 from mammalian skeletal muscle. Ca2+ release assay indicated that Chlo at high concentrations promoted Ca2+ release from sarcoplasmic reticulum through RyR1 channels. Single channel recording of purified RyR1 showed that Chlo activated RyR1 channel, increased channel open probability Po, reduced channel mean close time Tc, but did not change the channel mean open time To, suggesting that Chlo destabilized the closed RyR1 channel, rendered the channel easy to open. The dissociation constant Kd values of Chlo for RyR1 were of micromolar level, approximately 100-fold larger than that for insect RyR. The Kd values were smaller for open states than for closed/blocked states of the RyR1 channel. The maximal binding capacity Bmax did not change in the presence of either channel activators or inhibitors/blockers. Our results demonstrate that the insecticide Chlo is a weak activator of mammalian RyR1. It can interact with mammalian RyR1 and activate RyR1 channel but with much lower affinity compared with insect RyR; Chlo has a binding site distinct from all known RyR channel modulators and represents a novel type of RyR channel modulator. Our data provide biochemical and pharmacological insights into its high specificity to insect RyR and high selectivity of poisoning to insects over mammals.

Interactions between tetrahydroisoindoline-1,3-dione derivatives and human serum albumin via multiple spectroscopy techniques.

Some tetrahydroisoindoline-1,3-dione derivatives (TDDs) possess potent herbicidal activity. To assess possible impacts of TDDs on humans, the interactions between TDDs and human serum albumin (HSA) were evaluated with steady-state and time-resolved fluorescence spectroscopy, synchronous fluorescence spectroscopy, Fourier transform-infrared spectroscopy, and circular dichroism spectroscopy. The thermodynamic data obtained at temperatures of 298, 307, and 316 K indicate that TDDs spontaneously bind to HSA and thus form a TDD-HSA complex. The conformation and secondary structure of HSA are changed, and the intrinsic fluorescence of HSA is statically quenched by TDDs. Moreover, the TDD-HSA complex is formed primarily through electrostatic interactions and has only one binding site on HSA. A competitive ligand-binding assay revealed that site II (subdomain IIIA) displays the greatest affinity for TDDs. In addition, an acute toxicity bioassay showed no zebrafish mortality upon exposure to 4000 µg L-1 of TDDs. This work is helpful for understanding interactions between TDDs and HSA.

Cobalt-Catalyzed Enantioselective Negishi Cross-Coupling of Racemic α-Bromo Esters with Arylzincs.

The first cobalt-catalyzed enantioselective Negishi cross-coupling reaction, and the first arylation of α-halo esters with arylzinc halides, are disclosed. Employing a cobalt-bisoxazoline catalyst, various α-arylalkanoic esters were synthesized in excellent enantioselectivities and yields (up to 97 % ee and 98 % yield). A diverse range of functional groups, including ether, halide, thioether, silyl, amine, ester, acetal, amide, olefin and heteroaromatics is tolerated by this method. This method was suitable for gram-scale reactions, enabling the synthesis of (R)-xanthorrhizol with high enantiopurity. Radical clock experiments support the intermediacy of radicals.

Synthesis of Chrysogeside B from Halotolerant Fungus Penicillium and Its Antimicrobial Activities Evaluation.

Chrysogeside B, a natural cerebroside, was efficiently synthesized from commercial feedstocks. The bioassays showed that compounds 4, 5 and 6 exhibited enhanced biological activities compared Chrysogeside B. Further studies revealed that free hydroxyl groups and glycosidic bond have significant impact on the antimicrobial activities. The synthesis of Chrysogeside B and analogues designed to allow identification of the features of this glycolipid required for recognition by tested bacteria and Hela cells is described.

Comparative Studies of Interactions between Fluorodihydroquinazolin Derivatives and Human Serum Albumin with Fluorescence Spectroscopy.

In the present study, 3-(fluorobenzylideneamino)-6-chloro-1-(3,3-dimethylbutanoyl)-phenyl-2,3-dihydroquinazolin-4(1H)-one (FDQL) derivatives have been designed and synthesized to study the interaction between fluorine substituted dihydroquinazoline derivatives with human serum albumin (HSA) using fluorescence, circular dichroism and Fourier transform infrared spectroscopy. The results indicated that the FDQL could bind to HSA, induce conformation and the secondary structure changes of HSA, and quench the intrinsic fluorescence of HSA through a static quenching mechanism. The thermodynamic parameters, ΔH, ΔS, and ΔG, calculated at different temperatures, revealed that the binding was through spontaneous and hydrophobic forces and thus played major roles in the association. Based on the number of binding sites, it was considered that one molecule of FDQL could bind to a single site of HSA. Site marker competition experiments indicated that the reactive site of HSA to FDQL mainly located in site II (subdomain IIIA). The substitution by fluorine in the benzene ring could increase the interactions between FDQL and HSA to some extent in the proper temperature range through hydrophobic effect, and the substitution at meta-position enhanced the affinity greater than that at para- and ortho-positions.

Cobalt-bisoxazoline-catalyzed asymmetric Kumada cross-coupling of racemic α-bromo esters with aryl Grignard reagents.

The first cobalt-catalyzed asymmetric Kumada cross-coupling with high enantioselectivity has been developed. The reaction affords a unique strategy for the enantioselective arylation of α-bromo esters catalyzed by a cobalt-bisoxazoline complex. A variety of chiral α-arylalkanoic esters were prepared in excellent enantioselectivity and yield (up to 97% ee and 96% yield). The arylated products were transformed into α-arylcarboxylic acids and primary alcohols without erosion of ee. The new enantioenriched α-arylpropionic esters synthesized herein are potentially useful in the development of nonsteroidal anti-inflammatory drugs. This method was conducted on gram-scale and applied to the synthesis of highly enantioenriched (S)-fenoprofen and (S)-ar-turmerone.

A one-pot approach to pyridyl isothiocyanates from amines.

A one-pot preparation of pyridyl isothiocyanates (ITCs) from their corresponding amines has been developed. This method involves aqueous iron(III) chloride-mediated desulfurization of a dithiocarbamate salt that is generated in situ by treatment of an amine with carbon disulfide in the present of DABCO or sodium hydride. The choice of base is of decisive importance for the formation of the dithiocarbamate salts. This one-pot process works well for a wide range of pyridyl ITCs. Utilizing this protocol, some highly electron-deficient pyridyl and aryl ITCs are obtained in moderate to good yields.

Fluorescent probes for insect ryanodine receptors: candidate anthranilic diamides.

Diamide insecticides with high efficacy against pests and good environmental safety are broadly applied in crop protection. They act at a poorly-defined site in the very complex ryanodine (Ry) receptor (RyR) potentially accessible to a fluorescent probe. Two N-propynyl analogs of the major anthranilic diamide insecticides chlorantraniliprole (Chlo) and cyantraniliprole (Cyan) were accordingly synthesized and converted into two fluorescent ligands by click reaction coupling with 3-azido-7-hydroxy-2H-chromen-2-one. The new diamide analogs and fluorescent ligands were shown to be nearly as potent as Chlo and Cyan in inhibition of [3H]Chlo binding and stimulation of [3H]Ry binding in house fly thoracic muscle RyR. Although the newly synthesized compounds had only moderate activity in insect larvicidal activity assays, their high in vitro potency in a validated insect RyR binding assay encourages further development of fluorescent probes for insect RyRs.

Functional analysis of a point mutation in the ryanodine receptor of Plutella xylostella (L.) associated with resistance to chlorantraniliprole.

BACKGROUND: The diamondback moth, Plutella xylostella (L.) has developed extremely high resistance to chlorantraniliprole and other diamide insecticides in the field. A glycine to glutamic acid substitution (G4946E) in the P. xylostella ryanodine receptor (PxRyR) has been found in two resistant populations collected in Thailand and Philippines and was considered associated with the diamide insecticides resistance but no experimental evidence was provided. The present study aimed to clarify the function of the reported mutation in chlorantraniliprole resistance in P. xylostella. RESULTS: We identified the same mutation (G4946E) in PxRyR from four field collected chlorantraniliprole resistant populations of Plutella xylostella in China. Most importantly, we found that the frequency of the G4946E mutation is significantly correlated to the chlorantraniliprole resistance ratios in P. xylostella (R(2) = 0.82, P = 0.0003). Ligand binding assays showed that the binding affinities of the PxRyR to the chlorantraniliprole in three field resistant populations were 2.41-, 2.54- and 2.60-times lower than that in the susceptible one. CONCLUSION: For the first time we experimentally proved that the G4946E mutation in PxRyR confers resistance to chlorantraniliprole in Plutella xylostella. These findings pave the way for the complete understanding of the mechanisms of diamide insecticides resistance in insects.